Research efforts will continue to be directed toward elucidating eukaryote chromatin structure and function using micrococcal nuclease digestion dinetics, chemical cross-linking with reversible bifunctional reagents and gel electrophoresis, model building and X-ray diffraction. Studies of microccoccal muclease digestion kinetics will be continued and extended to include a more through examination of the effects of the history of the chromatin substrate with particular attention to exposure to chelating agents and ionic strength. The immediate goal of chemical cross-linking experiments is to resolve cross-linked histone dimers formed in nuclei into arginine rich and lysine rich histone fractions prior to electrophoretic analysis, in order to study the idenity and electrophoretic mobility of homodimers. X-ray diffraction experiments will depend on the prior success of reconstitution experiments now in progress.